I would think of a multilingual site (the interface) like a catalog or a simple
module for classified ads, where you can enter promotions.

The catalog would be with categories at various levels (subcategories)
that include description, price and images and the languages in which this is available.

We could have a separate category for those who wish to offer sources to download.
Programs or utilities that already exist but we would have everything centralized.

And another category for those who offer it under certain conditions eg. exchanges
or mutual collaboration: (Someone has a billing program and another an inventory prgm;
Together they integrate it and share it among themselves)